Fuel Cells, Hybrid power plant and
Power factor improvement
Understand and analyse Hybrid PV system, and
Power factor improvements.
3. Definition of Fuel Cell
• A fuel cell is an electrochemical device, which
converts chemical energy into an electrical energy
continuously till the fuel is supplied to the cell.
• A fuel cell generates an electrical energy due to
the reaction between fuel and oxidant with two
electrodes in presence of an electrolyte.
4. Classifications of Fuel cells
• According to the type of electrolyte used:
1. Alkaline fuel cell (AFC)
2. Phosphoric Acid Fuel Cell (PAFC)
3. Molten Carbonate Fuel Cell (MCFC)
4. Polymer Electrolytic Membrane Fuel cell (PEMFC)
5. Solid oxide fuel cell (SOFC)
5. • According to the type of fuel and oxidant used in the
• Hydrogen – oxygen fuel cell.
• Hydrogen – air fuel cell.
• Ammonia - air fuel cell.
• Synthetic gas - air fuel cell.
• Hydrocarbon (Gas)-air fuel cell.
• Hydrocarbon (Liquid) - air fuel cell.
6. • According to types of applications:
1. Space application fuel cell.
2. Vehicle propulsion fuel cell.
3. Submarine propulsion fuel cell.
4. Commercial fuel cell.
5. Cell used for defence application.
• On the basis of the nature of electrolyte :
1. Acidic electrolyte type.
2. Alkaline electrolyte type.
3. Neutral electrolyte type.
7. • On the basis of operating temperature :
1. Low temperature (below 150oC).
2. Medium temperature (150-200oC).
3. High temperature (250-800oC).
4. Very temperature (800-1100oC).
• Based on the physical state of the fuel cell:
1. Solid fuel cell
2. Liquid fuel cell
3. Gaseous Fuel cell
9. The arrangement of phosphoric acid fuel cell
componente is shown in Figure-1.
The electrodes are made of porous nickel material to collect
charges phosphoric acid is used as electrolyte. The porous
enable better contact between gas, electrolyte and
electrode for faster electrochemical reaction. It work on the
principle of that fuel (hydrogen) is into the anode side of the
cell. The fuel (hydrogen) is oxidized and liberated electrons
move to the external circuits.
10. The remaining positive hydrogen moves from
the anode into the electrolyte through porous cell
walls. The oxidant (oxygen) is fed into the cathode
side, Where it is reduced by the electrons coming
from anode through external circuit.
The negative oxygen ions and positive hydrogen
ions combine to form water.
11. Electrochemical reaction :
At anode : At the negative electrodes, hydrogen gas is converted to
hydrogen ions (H+) and an equal number of electrons (e-).
H2 →2H++2e- ------------ (1)
At cathode : The electrons originating at the negative electrode
flow through the external load to the positive electrode. Also, H+
ions migrate from negative electrode towards the positive
electrode through the electrolyte. On reaching the positive
electrode they interact with O2 to produce water.
½ O2 + 2H+ + 2e- →H2 O --------(2)
Combining the equations (1) & (2)
Fuel cell combines H2 andO2 to produce water.
H2+ 1/2O2 → H2 O
12. General specification of PAFC :
Fuel – Hydrogen.
Oxidant – Oxygen.
Electrolyte – Phosphoric acid
Electrodes – Porous Nickel.
Ideal emf - 1.23V at 25oC.
- 1.15 V at 200 oC.
Efficiency – 83%
Operating temperature - 150 oC - 200 oC
14. It works on the principle that its uses H2 or H2
rich gas as the fuel and oxygen or air as the oxidant,
uses 40% aqueous KOH (Potassium hydroxide ) as
electrolyte and electrodes used are porous nickel.
Operation : The operation and movements of charges
carries is shown in figure, Electrons are forced
through external circuit to cathode. At cathode,
oxygen gas water and electrons combine to produce
15. Electro Chemical reactions :
At cathode :
½ O2 + H2O +2e → 2OH −− − 1
At Anode :
These OH-migrate from the positive to the negative electrode
through the electrolyte. On reaching the positive electrode OH-
combine with H2 to produce water. An equivalent number of
electrons are that flow through the external load towards
H2 + 2OH → 2H2O + 2e ------------- (2)
Combining the equation (1) and (2) that fuel cell combines H2
and O2 to produce water.
H2 + ½ O2→H2O ----------------- (3)
16. General specification of AFC :
Fuel : Hydrogen or Hydrogen gas.
Oxidant : Oxygen or Air.
Electrode : Porous nickel
Electrolyte : 40% KOH.
Output : 1.23 at 90oC
18. Such fuel cells are also called solid polymer fuel cell (SPFC)
the fuel cell uses a solid membrane of organic materials
such as polystyrenes sulphuric acid as electrolyte. The
membrane has property to allow H+ ions to pass through
The desired properties of membrane are –
1. High ionic (H+) conductivity.
2. Non-permeable to reactant gases such as oxygen and
3. High resistance to dehydration.
4. Lesser tendency to electrosmosis.
5. High Amount of mechanical stability.
19. Electrochemical reactions :
At Anode :
+2e- ------ (1)
At Cathode :
Hydrogen ions formed at anode are transported to
cathode through proton exchange membrane and
electrons are forced through the outer circuit to
cathode. At cathode, ions, Electrons and oxygen gas
interact to produce water.
2H+2e- + ½ O2→ H2O ------(2)
Thus the overall reaction is –
H2 + ½ O2→ H2O ----------(3)
20. General specification of PEMFC :
Fuel : Hydrogen.
Oxidant : Oxygen or Air.
Electrodes : Deposited platinum layers.
Electrolyte : Proton conducting polymer membrane.
Output : 1.23V at 25 oC
21. Performance limiting factors of fuel cell
1.Reactivity :Reactivity is required because
electrodes of a fuel cell should have high electrode
activity so that they can generate high current
density. To have high electrode activity, electrodes
are made porous to increase the area of interface
between reactants, electrolyte and electrodes.
22. 2.Invariance : Invariance is required because a
fuel cell remains unchanged in it performance as
a converter of reaction to electric energy
throughout its working life. That is electrodes
should keep on acting as a perfect catalyst
without corrosion, Poisoning or any degradation.
Similarly , electrolyte should work without any
need for change of electrolyte and electrodes.
23. Losses of fuel cells :
• It is assumed that the losses of the fuel cells are
the losses at electrodes due to some sort of
• Basically polarization is the difference between
Theoretical and Actual output voltage.
• The losses at electrodes are mainly Three types-
1. Chemical Polarization or Activation polarization.
2. Concentration polarization.
3. Resistance polarization or ohmic polarization.
24. • The chemical polarization is a result of the way by
which ions are discharged and the rate of
discharge of ions at electrodes.
• Due to concentration polarization, the potential
decreases as the reactions can not maintain the
initial concentration at electrodes during current
• During reaction, ions move through electrolyte
which causes change in the conductivity of
electrolyte which is called resistance polarization
or ohmic polarization.
25. Advantages of fuel cells
1. High efficiency : Like generators and other engines , fuel
cells are energy conversion devices. They convert stored
energy within a fuel cell into usable energy. Fuel cells have
high conversion efficiency.
2. Low emission : Fuel cells emit considerably less emission.
3. It can be installed near the load point. There by reducing
the requirement of transmission lines.
4. Because of absence of moving part fuel cells are noiseless.
5. Fuel cells are non-polluting.
6. Fuel cells operating at low temperature have discharge at
low temperature.so require no cooling system.
7. Requires lesser time for installation and operation.
8. They require less area for installation.
9. They can meet varying load of customers.
26. Disadvantages / Limitations
1. Degradation of electrodes and electrolyte
reduces the performance of a fuel cell.
2. Initial cost is high.
3. Due to corrosion of electrodes causes low life
span of a fuel cell.
27. Applications of Fuel Cells
1. The fuel cells can be used as base load plants.
2. Small fuel cells can be used for residential
purposes at about 5 -10KW.
3. The fuel cells can be used in electric vehicles.
4. Distributed generation.
5. The fuel cells can also be used in space flight ,
space crafts as portable power plants.
28. Environmental Impact of fuel cells.
• In fuel cell hydrogen is used as fuel and oxygen or
air is used as oxidant with hydrogen as fuel , the
exhaust of a fuel cell contains only water vapour,
which not a pollutant, a part from some amount
• If air is used as oxidant, spent air , which is mostly
nitrogen , is also present in the exhaust. This is
again not a pollutant. No cooling water is required
as the generated heat can be easily utilized in a
cogeneration unit or discharged easily to the
29. • The heat can also be utilized, for fuel reforming
process. In case of hydrocarbon fuels, CO2 is also
produced. However, as the fuel is used more
efficiently , the amount of CO2 emission is less
compared to that when the same fuel is used in
conventional thermal plants with the same
output. Pollutants are negligible compared to
conventional thermal plants.
30. Hybrid PV systems
Hybrid system : Whenever a system consists more than
one type of the power sources, such a system is called
Hybrid PV system : When hybrid system consists PV
system as a main energy source along with at least one
more other source, then such a system is called hybrid
• Types of hybrid PV systems
1. PV-Diesel hybrid system
2. PV-Wind hybrid system
3. PV-fuel cell hybrid system.
32. The output of diesel generator is rectified using
AC-DC converter and it is connected to DC link. To
fed AC load, The DC is converted to AC using
The output of PV array is also connected to DC link
through DC-DC converter.
The battery is connected which not only store
excess power but supplies the power when load
changes and during diesel generator start-up.
It is necessary to design inverter for matching
maximum load requirement.
34. • The PV-wind hybrid system. In this system the
output of the PV array and rectifier out of the
wind generator are connected in parallel,
Because variation in the wind velocity results
into large changes in the frequency and output
power of the generator.
• The drawback of this system is that system is
that PV and wind both are unreliable sources
and hence to meet the load demand a large
battery bank is needed.
36. • In this case two separate DC-DC converter are
needed and are connected in parallel. One of
these is fed from PV array, While the other is fed
from fuel cells.
• The DC-DC converter is operated to obtain the
maximum power from PV array. Advantage of
such system is that easy synchronization as
compared to the synchronization at the two AC
38. • Meaning of power factor :
The cosine of angle between voltage and current
in an A.C circuit is know as power factor.
The electrical energy generated, transmitted and
distributed in the form of alternating current. Most of
the loads such as induction motor, arc lamps etc., are
inductive loads and hence have low lagging power
factor, Low power cause increase in current which
results in additional losses. It is important to maintain
power factor close to unity.
39. Power factor Analysis :
Power drawn by the A.C inductive circuit can
shown with a power triangle as follows:
40. • OA=VI COS Ø (Active Power) in KW.
• AB= VI Sin Ø (Reactive power) in KVAR.
• OB= VI (apparent power) in KVA.
Apparent power OB= 𝑂𝐴2 + AB2
or KVA2 = KW2 + KVAR2
Apparent power2 = Active power2 +Reactive power2
Power factor , cos Ø =
41. Significance of Power Factor improvements
• The improvement of power factor is very important
for both consumer and generating station:
• For consumers: A consumer has to pay electricity
charges for his maximum demand in KVA plus the
units consumed. Improvement of p.f to a proper
value results in annual saving of the consumer.
• For Generating station : The generators are rated in
KVA but useful output power depends on KW. As
station output is KW = KVA × P.f . Therefore number
of units supplied by it depends upon the power
42. Causes of low power factor :
Low power factor is undesirable from economic point of view.
The following are the causes of low power factor :
1. Most of the industrial motors are induction type, they have
low lagging power factor. These motors work at extremely
low power factor (0.2-0.3) on light load and at 0.8 to 0.9 at
2. Arc lamp, electric discharge lamps and industrial heating
furnaces operate at low lagging power factor.
3. The load on the power system is varying, being high
during morning and evening , low all other times. During
low load period , supply voltage is increased which
increases the magnetization current. This decreases
43. Effects of low power factor on power plant
For a 3-phase balanced system. Load current is given by :
3 𝑉 𝐶𝑂𝑆Ø
If P and V are constant, the load current , IL is inversely
proportional to power factor that is lower the power
factor, higher the current and vice-versa.
44. • Large KVA rating of equipment : The
electrical machinery (e.g. : alternator ,
transformer , switchgear ) is always rated in
It is clear that kVA rating of the equipment is
inversely proportional to power factor. The
smaller the power factor , the larger is the kVA
rating . Therefore , at low power factor, the kVA
rating of the equipment has to be made more,
making the equipment larger and expensive.
45. • Greater conductor size : To transmit or distribute
a fixed amount of power at constant voltage, the
conductor will have to carry more current at low
power factor . This necessitates large conductor
• Large copper losses : The large current at low
power factor causes more I2R losses in all the
elements of the supply system. This results in
• Poor voltage regulation : The large current at
low lagging power factor causes greater voltage
drop in alternator, transformers, transmission
lines and distributors. Hence poor voltage
46. • Reduced handling capacity of system: The
lagging power factor reduces the handling
capacity of all the elements of the system. It is
because the reactive component of current
prevent s the full utilization of installed capacity.
47. Methods of power factor improvement.
1. Static capacitor
2. Synchronous condenser.
3. Phase advancers.
48. 1.Static capacitor
The power factor can be improved by connecting capacitors in parallel
with the equipment operating at lagging power factor. The capacitor
draw a leading current and partly or completely neutralizes the lagging
reactive component of load current. This raise the power factor of the
load. For three phase load, the capacitors can be connected in delta or
star as shown in figure. Static capacitor are invariably used for power
factor improvement in factories.
49. 2.Synchronous condenser.
A synchronous motor take a leading current when over-
excited and , therefore , behaves as a capacitor. An over-
excited synchronous motor running on no load is know as
synchronous condenser. When such a machine is connected
in parallel with the supply, it take a leading current which
partly neutralizes the lagging reactive component of the
load thus the power factor is improved.
50. 3.Phase advancers.
• Phase advancers are used to improve the power factor of
induction motors. The low power factor of an induction
motor is due to fact that its stator winding draws exciting
current which lags behind the supply voltage by 900 .
• If the exciting ampere turns can be provided from some
other A.C source, then the stator winding will be relieved
of exciting current and the power factor of the motor can
51. • The phase advancer is mounted on the same
shaft as the main motor and is connected in the
rotor circuit of the motor. It provides exciting
ampere turns to the rotor circuit at slip
frequency. By providing more ampere turns than
required, the induction motor can be made to
operate on leading power factor like an over
excited synchronous motor.
53. Consider an inductive load taking a lagging
current I at a power factor cosØ1. in order to
improve the power factor of this circuit, the
remedy is to connect such an equipment in
parallel with the load which takes a leading
reactive component and partly cancels the
lagging reactive component of the load.
54. • Fig 1. shows a capacitor connected across the
load. The capacitor takes a current Ic which
leads the supply voltage V by 900 . The current
Ic partly cancels the lagging reactive component
of the load current as shown in phasor diagram
• The resultant circuit current becomes I’ and its
angle of lag Ø2. it is clear that Ø2 is less than Ø1
so that new p.f cos Ø2 is more than the
previous p.f cos Ø1.
55. From the phasor diagram, it is clear that after p.f
correction, the lagging reactive component of the
load is reduced to I’sin Ø1.
I’sin Ø2 = I sin Ø1 – Ic
Or Ic = I sin Ø1 - I’sin Ø2
∴ capacitance of capacitor to improve p.f from
57. Model Questions
• Cognitive Level: UNDERSTAND
1. Define fuel cell. And Classification of fuel cells.
2. Explain the Working principle and operation of
phosphoric acid fuel cell (PAFC).
3. List the Advantages of fuel cells.
4. List the Applications
5. List the Causes of low power factor.
6. Mention the effects of low power factor on power
7. Explain selection of capacitor bank to improve power
8. Explain the Losses of fuel cells,
58. • Cognitive Level: APPLICATION
1. Explain the Working principle and operation of alkaline fuel cell
2. Explain the Working principle and operation of polymer Electrolyte
Membrane fuel cell
4. Explain the performance limiting factors of fuel cell.
5. Explain the Environmental Impact of fuel cells.
6. Explain Hybrid PV systems. Types of hybrid PV systems.
7. Explain with block diagram the construction and working of PV-
Diesel hybrid system,
8. Explain with block diagram the construction and working of PV-
Wind hybrid system
9. Explain with block diagram the construction and working of PV-fuel
cell hybrid system.
10. Explain the Meaning of power factor and its significance.